The present invention generally relates to variable flow electrically controlled valves.
When it is desired to control the flow rate of a liquid or gaseous fluid, a variable valve controlled, for example, electrically, is used. Such a variable flow valve comprises an aperture that is variable between a minimum value, for example a zero value corresponding to the closed valve, and a maximum value corresponding to a completely open valve. An electromagnetic device, for example an electromagnet or an electric motor, controls the aperture value of the valve.
The invention more particularly relates to electrically controlled valves of a simple and inexpensive design, these valves being liable to be used in apparatuses manufactured in mass production and at a low cost.
The invention more precisely relates to a specific type of valve comprising a tube of elastic material to which is associated a control mechanism generating a variable elastic flattening of the tube to control the flow rate of a fluid flowing through the tube. When the tube is fully flattened, it is obstructed and the valve is in its closed position.
This type of valve enables to continuously control the flow rate of a fluid between a zero and a maximum value. The control mechanism must adjust the position of a part designed to pinch the tube. To achieve such a position adjustment, conventional means used in the art are complex. For example, as disclosed in U.S. Pat. No. 4,397,642, a stepper motor is servo-controlled as a function of the flow measured in a pinched tube by a sensor. A stepper motor, associated only to its driver circuit, is already expensive in itself. An additional servo-control system makes the cost prohibitive for mass produced apparatuses.